The BBC has uncovered details of a secret deal that let hundreds of IS fighters and their families escape from Raqqa, under the gaze of the US and British-led coalition and Kurdish-led forces who control the city.

A convoy included some of IS’s most notorious members and – despite reassurances – dozens of foreign fighters. Some of those have spread out across Syria, even making it as far as Turkey.

Lorry driver Abu Fawzi thought it was going to be just another job.

He drives an 18-wheeler across some of the most dangerous territory in northern Syria. Bombed-out bridges, deep desert sand, even government forces and so-called Islamic State fighters don’t stand in the way of a delivery.

But this time, his load was to be human cargo. The Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab fighters opposed to IS, wanted him to lead a convoy that would take hundreds of families displaced by fighting from the town of Tabqa on the Euphrates river to a camp further north.

The job would take six hours, maximum – or at least that's what he was told.

But when he and his fellow drivers assembled their convoy early on 12 October, they realised they had been lied to.

Instead, it would take three days of hard driving, carrying a deadly cargo - hundreds of IS fighters, their families and tonnes of weapons and ammunition.